Pat your chicken dry with a paper towel and season lightly with salt and pepper. Arrange the pieces in a single layer in your baking dish, leaving a little space between each piece. This helps the chicken cook evenly instead of steaming.
Set your oven to 400°F and let it fully preheat before the dish goes in. A hot oven from the start locks in juiciness and helps the cheese get that golden, bubbly finish everyone loves.
Spoon the pesto generously over each piece of chicken, using the back of your spoon to spread it into an even layer. Don't be shy here, the pesto is what infuses the chicken with all that garlicky, herby flavor.
Place your tomato slices over the pesto layer, then top everything with mozzarella. Finish with a sprinkle of parmesan and a dusting of Italian seasoning. This order keeps the cheese from sliding off during baking.
Slide the dish into your preheated oven and bake for 30-35 minutes, or until the chicken reaches 165°F internally and the cheese is melted and lightly browned. Thicker chicken breasts may need a few extra minutes.
Let the dish rest for 5 minutes once it's out of the oven this keeps the juices in the chicken instead of on your cutting board. Scatter fresh basil leaves on top right before serving for a burst of color and aroma.